1. Field of the Invention
The present invention relates to transducers for sound reproduction, and, more particularly, to low frequency loudspeaker drivers, conventionally referred to as woofers.
2. Discussion of the Prior Art
A great variety of moving coil loudspeaker designs have been proposed for high quality low frequency sound reproduction, many have gone into commercial use. These are typically included in a modern full range loudspeaker system utilizing different speakers for different segments of the sound spectrum. For example, a “woofer” is used for bass or low frequencies, a mid-range speaker is used for intermediate frequencies and a “tweeter” is used for the highest frequencies in the reproduced spectrum.
It is generally accepted that loudspeakers with sufficient size to produce adequate bass have well understood limitations. In particular, high power signals driving the cone into extreme excursions cause poor sound reproduction when driven by more challenging audio signals.
Typical prior art woofers utilize circular baskets supporting frustoconical driver diaphragms having a circular peripheral edge carrying an annular surround or suspension. Customarily, the circular small end of the frustoconical diaphragm supports a cylindrical voice coil former upon which is wound a conductive voice coil having positive and negative terminal ends. Conventional woofers utilize baskets which closely follow the frustoconical shape of the driver diaphragm and support the motor magnet and the circular diaphragm surround in an co-axial alignment, permitting the axial movement of the diaphragm in response to electrical excitation of the voice coil.
In some high-end automotive or twelve volt applications, music afficionados and auto-sound competitors will install several woofers in a two-dimensional array on a baffle or enclosure surface; for example, it may be desirable to install four or six woofers in two rows of two or three.
Another concern for music afficionados and auto-sound competitors is woofer failure due to thermal or mechanical overloading problems. Substantial amounts of power are required to provide competition-winning sound pressure levels, often well over 150 decibels (dB). Signals having such power require very large current flow through voice coil conductors, thus generating substantial amounts of heat, and drive the woofers to extreme excursions, thus generating extreme mechanical loads on diaphragms and suspensions.
In Sound Pressure Level (SPL) competitions, competitors seek the loudest possible playback and often over-drive the loudspeaker drivers, causing voice coils to burn out or open circuit. Such extreme use (or abuse) may also cause mechanical failure of the cone, the surround, or the “spider” suspension member. Competitors have become accustomed to replacing failed drivers, often accumulating piles of failed drivers during the course of a competition.
In order to overcome these perceived difficulties, the inventor has developed a number of new woofer configurations and parts configurations.